JPH0516196A - Method for monitoring of injection molding machine - Google Patents

Abstract

PURPOSE:To make it possible to judge automatically the quality of a molded item having high accuracy reflecting the plasticized condition of a resin in some extent. CONSTITUTION:The whole section of the primary injection process wherein a molten resin is injected and filled in a cavity or at least the last section of the primary injection process is performed by pressure control by means of a loading pressure controlling valve 6 based on a set loading pressure set in accordance with the forwarding position of a piston rod 5a of an injection cylinder 5 and the injection speed during the process section by this pressure control is actually measured and it is compared with the value in an allowable range to perform a judgement of the quality.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring an injection molding machine using an injection cylinder (hydraulic cylinder) as an injection actuator.

[0002]

2. Description of the Related Art In this type of hydraulically driven injection molding machine, a mold clamping cylinder (hydraulic cylinder) is used to perform mold clamping, and the injection cylinder (hydraulic cylinder) clamps molten resin at an appropriate injection timing thereafter. The mold is injected and filled into a molding space (cavity), and after a predetermined cooling time, the mold is opened to take out the molded product.

In recent years, in such an injection molding machine, for example, a microcomputer that controls the entire machine captures actual measurement data of various molding operation conditions for each shot during continuous operation, and the captured actual measurement data is obtained. The microcomputer determines whether or not it is within the preset allowable range and automatically determines the quality of the molded product.
Machines that perform quality control of molded products based on monitor data are becoming popular.

[0004]

In the machine (injection molding machine) having the above-mentioned monitoring function, the monitor items taken in as the actual measurement data (monitor data) of the molding operation conditions are, for example, time monitoring items and position monitoring. Items include rotational speed monitoring items, speed monitoring items, pressure monitoring items, temperature monitoring items, and power monitoring items, and technological innovations such as sensors have enabled relatively accurate sensing. However, in the field of injection molding machines, a complete analysis of the detailed resin behavior mechanism has not been achieved at this time, and although this research is in progress, the plasticized state of the resin is regarded as a black box. Is the current situation. Therefore, it is practically difficult to monitor the plasticized state of the resin, and it has been desired to develop a machine capable of highly accurately judging the quality of a molded product that reflects the plasticized state of the resin.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a method of monitoring an injection molding machine, which can accurately judge whether a molded product is good or bad, which reflects the plasticized state of the resin to some extent.

[0006]

In order to achieve the above object, the present invention provides a method for monitoring an injection molding machine in which pressure oil from a hydraulic pump or an accumulator is supplied to an injection cylinder to perform injection. A load pressure control valve that is directly connected to the oil chamber and controls the hydraulic pressure supplied to the forward oil chamber is provided, and the entire primary injection stroke for injecting and filling the molten resin into the cavity, or at least the primary injection stroke The end section of the above is executed by pressure control by the load pressure control valve based on the set load pressure set according to the forward position of the piston rod of the injection cylinder, and the injection speed in the stroke section by this pressure control is measured. To monitor the change of state.

[0007]

[Operation] A load pressure control valve consisting of an electromagnetic proportional relief valve for controlling the hydraulic pressure supplied to the forward oil chamber of the injection cylinder is provided, and the entire section of the primary injection stroke (injection / filling stroke),
Alternatively, at least in the final stage of the primary injection stroke, the injection / filling stroke is controlled by the load pressure control valve by pressure control based on each set load pressure set according to the forward position of the piston rod of the hydraulic cylinder, regardless of the speed. To execute. As a result, in the injection / filling stroke section by pressure control, the hydraulic pressure (load pressure) supplied to the injection cylinder is controlled so as to match the set load pressure, and the injection speed depends on the load pressure. Indirectly controlled by form. That is, in the injection / filling stroke section under pressure control, the injection speed is not directly controlled, so it changes according to the resin plasticization state change corresponding to the resin temperature or mold temperature change, and the resin temperature, mold temperature, etc. The higher the temperature becomes, the lower the viscosity of the molten resin becomes, so the injection speed becomes faster than the reference value, and the lower the resin temperature or mold temperature becomes, the higher the viscosity of the molten resin becomes, and the injection speed becomes slower than the reference value. .. Therefore, by measuring the injection speed in the injection / filling stroke section by pressure control and comparing it with the allowable value, it becomes possible to judge the quality of the molded product that reflects the plasticized state of the resin to some extent, and a more accurate monitoring function It is possible to realize a machine with.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory diagram showing a hydraulic circuit and a control system of an injection cylinder system of an injection molding machine according to the present embodiment, and FIG. 2 is a load pressure (injection cylinder 5) during an injection / filling stroke.
FIG. 6 is a graph showing the relationship between the pressure of the forward oil chamber) and the injection speed.

In FIG. 1, 1 is a hydraulic pump, 2 is a pressure control valve (electromagnetic proportional relief valve) that regulates the upper limit of the pressure oil discharged from the hydraulic pump 1, and 3 is the valve opening degree. A flow rate control valve for controlling the flow rate by means of 4, a direction switching valve for controlling the moving direction of the piston rod of the injection cylinder, 5 an injection cylinder (hydraulic cylinder), 5a not shown, and a screw screw in the heating cylinder The piston rod of the injection cylinder connected by the means is connected to the oil passage between the flow control valve 3 and the advancing oil chamber of the injection cylinder 5 (downstream oil passage seen from the flow control valve 3). Installed load pressure control valve (electromagnetic proportional relief valve), 7 is piston rod 5a
Is an injection stroke detection sensor (for example, an encoder) that detects the position of.

Reference numeral 8 denotes a microcomputer for controlling the entire machine, including a molding operation condition setting storage unit 9,
A molding process control unit 10, a measured data storage unit 11, an allowable range setting storage unit 12, a molded product quality determination unit 13, and the like are provided. Then, while referring to the set values of various operating conditions stored and set in advance in the molding operating condition setting storage unit 9 and the actual measurement data of various operating conditions of the current shot captured in the actual measurement data storage unit 11, the molding process is performed. The control unit 10 drives and controls a hydraulic system control target including an electromagnetic control valve group, an electric control target including an electromagnetic motor, a heater, etc. through a driver circuit group (not shown) based on a molding operation control program created in advance. However, the machine is made to perform a series of molding operations. That is, the electromagnetic control valve group 2,
The microcomputers 3, 4 and 6 can be independently controlled by the microcomputer 8 via appropriate driver circuits (not shown), and the flow control valve 3 is controlled in response to a command from the microcomputer 8.
The speed (flow rate corresponding to the speed) and the hydraulic pressure upper limit value by the pressure control valves 2 and 6 can be variably set, and the switching position of the direction switching valve 4 can be selected.

The measurement data S from the injection stroke detection sensor 7 is stored in the measured data storage section 11 of the microcomputer 8.
1 and the measurement information S2 to SN from various sensor groups (not shown) arranged in each part of the machine are appropriately subjected to conversion processing and taken in.
The microcomputer 8 grasps actual measurement information such as position, pressure, rotation speed, temperature, and electric power, and further measures time by a clock function built in itself, and calculates speed from position information and time information to measure speed. Information is also measured data storage unit 11
It is designed to be stored in. That is, the measurement data by the injection stroke detection sensor 7 is taken into the microcomputer 8 and is recognized as an injection stroke (position), and the injection speed is also calculated and recognized.

The allowable range setting storage unit 12 of the microcomputer 8
In the actual measurement data stored in the actual measurement data storage unit 11 as described above, the permissible range data set in advance by a case study corresponding to each item defined as a monitor item is stored. Molded product quality determination unit 13
However, by comparing the actual measurement data for monitoring in the actual measurement data storage unit 11 with the allowable range data in the allowable range setting storage unit 12, the quality of the molded product is automatically determined for each shot before the process of taking out the molded product. It is supposed to do. Then, when the molded product quality determination unit 13 makes a non-defective product determination, the molding process control unit 10 is notified of this, and the molded product taken out by the molded product take-out mechanism (not shown) is placed on the non-defective product placement location. When the molded product quality determination unit 13 makes a defective product determination, the molding process control unit 10 is also informed of this fact and the molded product taken out by the molded product take-out mechanism (not shown) is placed in the defective product storage. It is like this.

Here, in the present embodiment, as shown in FIG. 1, the load pressure control valve 6 is directly connected to the advancing oil chamber of the injection cylinder 5 in an oil passage downstream of the flow control valve 3. Since the injection / filling control that prioritizes speed by the flow rate control valve 3 is not performed, the pressure control valve 2 is set to the maximum pressure and the flow rate control valve 3 is set to the maximum flow rate. It is possible to perform injection / filling (primary injection) control that prioritizes the hydraulic pressure (load pressure) according to the hydraulic pressure upper limit value that is variably set by the control valve 6. During the injection / filling operation by pressure control described below, the microcomputer 8 sets the pressure control valve 2 to the maximum pressure and the flow rate control valve 3 to the maximum flow rate.

In the above structure, the directional switching valve 4 is switched from the neutral position to the left position at a timing after a predetermined time has elapsed after the completion of mold clamping, and the pressure oil from the hydraulic pump 1 is injected into the injection cylinder 5. Is supplied to the forward advancing oil chamber, whereby the screw (not shown) is integrally advanced together with the piston rod 5a, and the molten resin is also blown between the die clamped from the nozzle at the tip of the heating cylinder (not shown). The cavity (molding space) begins to be injected and filled. At the time of this injection / filling stroke (primary injection stroke), the preset load pressure is preset for each zone A, B, C, D into which the injection / filling section (injection stroke) is arbitrarily divided as shown in FIG. And the forward stroke position detection information by the injection stroke detection sensor 7, the upper limit regulation value by the load pressure control valve 6 is variably controlled by the command of the microcomputer 8 described above, whereby the load pressure (filling pressure as injection pressure) is changed. The injection / filling process is executed by controlling. That is, as shown in FIG. 2, in the injection / filling stroke (primary injection stroke) section, the injection / filling stroke is executed by pressure control that substantially follows the set load pressure regardless of the injection speed. During the filling process (primary injection process), the load pressure is made to match the set load pressure to maintain a stable filling pressure. When injection / filling is performed based on pressure control that matches the set load pressure, the injection speed is indirectly controlled in a form that depends on the load pressure. Therefore, by setting the set load pressure to an arbitrary characteristic line, it is possible to obtain a desired injection speed curve to some extent, though not exactly. When it is recognized from the measurement information of the injection stroke detection sensor 7 that the piston rod 5a has reached the end position of the injection / filling stroke section (that is, has reached the holding pressure switching point), the microcomputer 8 , A pressure holding process for performing pressure control according to time is entered, and the upper pressure limit value of the load pressure control valve 6 is controlled to a pressure holding set value to carry out a pressure holding process for a predetermined time.

Here, if the measured injection speed data in the injection / filling stroke (primary injection stroke) section is shown by, for example, the solid line in FIG. The higher the temperature becomes, the lower the viscosity of the molten resin becomes, so the measured injection speed data becomes faster than the reference value (solid line data in FIG. 2) as indicated by the two-dot chain line in FIG. 2, and conversely the resin temperature, mold temperature, etc. As the viscosity decreases, the measured injection speed data becomes slower than the reference value (solid line data in FIG. 2) as indicated by the one-dot chain line in FIG. In the present embodiment, the injection based on such pressure control
The measured injection speed data at the time of the filling process is taken in by the measured value data storage unit 11 of the microcomputer 8, and the measured injection speed data and the allowable range data stored in the allowable range setting storage unit 12 are used to determine whether the molded product is good or bad. However, since it is one of the monitoring items for the quality judgment, it is possible to judge the quality of the molded product that reflects the plasticized state of the resin to some extent, and it is possible to realize a machine having a more accurate monitoring function.

FIG. 3 is a load pressure (pressure in the forward oil chamber of the injection cylinder 5) at the injection / filling stroke by another control method of the injection / filling stroke (primary injection stroke) executed by the configuration of FIG.
It is a graph which shows the relationship between and injection speed. In the example shown in FIG. 3, the injection / filling stroke section (primary injection stroke section)
Is divided into a first injection / filling stroke section and a second injection / filling section following the first injection / filling stroke section. In the first injection / filling stroke section, the piston rod 5a of the injection cylinder 5 is irrespective of the load pressure. The injection / filling stroke is executed by the speed control by the flow rate control valve 3 based on the speed set according to the advance position, and the piston rod 5a is moved to the advance position regardless of the speed in the second injection / filling section. The injection / filling stroke is executed by the pressure control by the load pressure control valve 6 similar to the above based on the suitable filling pressure set accordingly. As described above, even when the injection / filling stroke is executed by the pressure control only in the final section of the injection / filling stroke (primary injection stroke), as shown in FIG. The higher the temperature, the lower the viscosity of the molten resin.
As indicated by the dashed line, the value becomes larger than the reference value (solid line data in FIG. 3), and conversely, when the resin temperature, mold temperature, etc., decreases, the viscosity of the molten resin increases, so the measured injection speed data is one point in FIG. Reference value as indicated by the chain line (solid line data in Figure 3)
Will be smaller than. Therefore, by monitoring the actually measured injection speed data in the final section of the injection / filling process (primary injection process), it is possible to automatically determine the quality of the molded product which also reflects the plasticized state of the resin to some extent.

In the above embodiment, a hydraulic pump is used as a pressure oil supply source for injection, but as shown in FIG. 4, this is suitable for high-speed injection as a pressure oil supply source dedicated to injection. Of course, the accumulator 14 can be substituted, and in the case where the entire section of the primary injection stroke is executed based on the pressure control as shown in FIG. 2, such a hydraulic circuit dedicated to injection can be provided. good. Here, in FIG. 4, 15 is a switching valve.

[0018]

As described above, according to the present invention, it is possible to provide a monitoring method for an injection molding machine, which is capable of highly accurately judging the quality of a molded product that reflects the plasticized state of the resin to some extent, and its value is great.

[Brief description of drawings]

FIG. 1 is an explanatory view of essential parts showing a hydraulic circuit and a control system of an injection cylinder system of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a graph showing a load pressure and an injection speed during an injection / filling stroke when the first control mode according to an embodiment of the present invention is adopted.

FIG. 3 is a graph diagram showing a load pressure and an injection speed during an injection / filling stroke when a second control mode according to an embodiment of the present invention is adopted.

FIG. 4 is an explanatory diagram showing a hydraulic circuit of an injection cylinder system of an injection molding machine according to another embodiment of the present invention.

[Explanation of symbols]

 1 Hydraulic Pump 2 Pressure Control Valve 3 Flow Control Valve 4 Direction Switching Valve 5 Injection Cylinder 5a Piston Rod 6 Load Pressure Control Valve 7 Injection Stroke Detection Sensor 8 Microcomputer (Microcomputer) 9 Molding Operation Condition Setting Storage 10 Molding Process Control 11 Measured data storage unit 12 Allowable range setting storage unit 13 Molded product quality judgment unit 14 Accumulator 15 Switching valve

Claims (1)

Claim: What is claimed is: 1. An injection molding machine for supplying pressure oil from a hydraulic pump or an accumulator to an injection cylinder for injection, wherein the advance oil is directly connected to an advance oil chamber of the injection cylinder. A load pressure control valve for controlling the hydraulic pressure supplied to the chamber is provided, and the entire section of the primary injection stroke for injecting and filling the molten resin into the cavity, or at least the final section of the primary injection stroke,
It is executed by pressure control by the load pressure control valve based on the set load pressure set according to the forward position of the piston rod of the injection cylinder, and the state change is performed by actually measuring the injection speed in the stroke section by this pressure control. A method for monitoring an injection molding machine, which is characterized by being monitored.